1. Field of the Invention
The present invention relates to an exhaust treatment device, which may, for example comprise a catalytic device having a one-piece cylindrical housing, preferably formed of metal, with integral inlet gas shields and diffusers which may be spin-formed.
2. Disclosure Information
The tailpipe emission control laws applicable to automotive vehicles in various countries are becoming increasingly stringent. Tighter standards demand more precise air/fuel ratio control. This is possible only if air leaks in the exhaust system are kept to an absolute minimum, because air leaks cause a loss of air/fuel ratio control capability. A second important consideration relates to the need to rapidly "light off" exhaust treatment devices. Rapid light off requires that certain exhaust treatment devices be located close to the vehicle's engine. Thus, it is highly desirable to have an exhaust treatment device which packages in an extremely small volume, and which, therefore, may be mounted in engine compartment or the toeboard area of a vehicle, or in other areas which do not offer much space for an exhaust treatment device.
Another objective of automotive manufacturers is to reduce cost of vehicles; engine exhaust treatment systems comprise an expensive vehicle system. The present exhaust treatment device, while allowing much more flexible packaging, also allows lower cost because welding and additional parts are eliminated.
U.S. Pat. No. 4,969,264 discloses a catalytic converter and substrate support having a swaged center section and ram-formed ends. Unfortunately, the design of the '264 patent is not suitable for use as an automotive catalytic converter because the ram-formed ends do not provide any protection against undercutting of the support system by the exhaust gases. And, ram forming in close proximity to a catalyst substrate may have the unfortunate consequence of breaking the substrate.
The inventors of the present device have determined that a segmented inlet gas shield and diffuser may be spin-formed rather than ram-formed so as to provide a gas shield, greatly reducing exhaust gas impingement upon the catalytic substrate sealing and support system, while also producing a device of leakproof construction and with a reduced package volume. Additionally, an exhaust treatment device, according to the present invention, having integral diffusers, may be mated with exhaust pipes without a need for additional extensions.